3G Network Roll-Out Vision, Challenge and · PDF file3G Network Roll-Out Vision, Challenge and Solution ... Makes it difficult to have various coverage ... factor to look for is downtilt

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Network Performance for Profitability

Design – Optimize – Business Improvement

3G Network Roll-Out Vision, Challenge and Solution

LS Telcom Summit 2005June 8th, 2005

Bernard Breton, Vice President Research & Development

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Rolling Out 3G Networks

Goal is to explain:

- Review of 3G Roll-Out Philosophies

- Preparing for initial commercial launch

- Performing pre-launch optimization

- Post-launch network optimization

- Conclusion & Discussions

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For each GSM macro-cell, a WCDMA cell is deployedAdvantages

Easy to rollout (almost no rollout considerations)Easy to outsource (simple design criteria)Works reasonably well if there are no GSM capacity cells

DisadvantagesHigher initial CAPEXLower performance levelsDoes not work with all sites – some GSM sites just can’t be re-usedMore complex and expensive post-launch optimizationMakes it difficult to have various coverage objectives (no control over it)

1:1 Overlay Approach

3G Roll-Out Philosophy: 1:1 Overlay

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1:1 Rollout Process

Install all Node B of a cluster

Integrate all new Node B

Drive test area

Optimize radio parameters

For each GSM BTS for a given cluster, a WCDMA Node B is installed. If dual-band antennas are installed, then the existing antenna is replaced with a new dual band antenna

When a group of Node B (cluster) is enabled, various system parameters (GSM and WCDMA) must be updated. This is particularly true for the neighbor relations in order to provide good handover performance

Most vendors rely heavily on drive test to drive the manual optimization process in order to achieve agreed KPIs. Drive tests can also be utilized to improve predictions when using an automated network optimization solution (ACP)

Antenna configuration, power settings and neighbor relations can be optimized based on drive test and/or predictions. Automatic or manual techniques can be used

Coverage/Quality objectives are truly only dealt with during the optimization phase


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Link Budget Comparison

15 dBiBS Antenna Gain

144 dBMax. Path Loss

24 dBmMS EIRP

-105 dBmSensitivity

12 dBTarget C/N

4 dBBS Noise Figure

-121 dBmNoise

-174 dBm/HzNoise Density

200 kHzBandwidth

GSM Link Budget

139142150Max. Path Loss: dB(no loading)

777Service margin: dB

-111-113-122BTS Sensitivity: dBm

357Target Eb/Nt: dB

101425Processing gain: dB

-105-105-105Noise: dBm

-174-174-174Noise density: dBm/Hz

38414412.2Data rate: kbps

UMTS Link Budget

Voice DCS 1800 and UMTS 64/144 kbps link budgets are very similar


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Excessive Pollution in 1:1 Re-use Model1:1 Overlay Approach

Large areas with a very low spectral efficiency and poor Ec/Io

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Coverage & Capacity Considerations

Given that the link budgets are reasonably compatible between DCS1800 and WCDMA, the average cell spacing will be adequateIt remains a utopian concept to think that a simple 1:1 re-use is feasible

Almost certainly, capacity cells do exist in urban areas (particularly true in 900)Excessive propagation can be solved in GSM with proper frequency planning. This is nowhere as easy in WCDMAIn fact, hierarchical cell structures are often used to provide a trade-off between coverage and capacitySuch structure does not work in WCDMA

Key initial problem with a 1:1 re-use will be the presence of a small (but important) number of substantial polluters, leading to a lower capacity and quality


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WCDMA link budget is very dependent upon the actual network load (i.e. cell breathing effect)During busy hours, the high-data rate coverage will therefore suffer quite substantially (E.g. 384kbps allowable path loss restricted to 132 dB at 75% - about 10 dB worst than GSM)Voice link budget remains better (or equal to) GSM even when loading is quite high ( > 75 % )This translates to a network with solid voice coverage and fluctuating high data rate coverage

Might make it difficult to sell the value of high-data rate services when they are only solid during the quiet times


Coverage Considerations of a Loaded Network

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Cell Breathing Impact on UMTS Coverage1:1 Overlay Approach

Voic

e14

4 kb

ps10% Network Load 75% Network Load

Probability ofService

> 99%

> 95%

> 90%

> 50%

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Cell Breathing Impact : StatisticsService Coverage Comparison

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

Voice 10% Voice 75% 144 10% 144 75% 384 10% 384 75%

Service & Loading

Per

cent

age

of c

alls below 50

50 to 7575 to 9090 to 9595 to 9999 to 100

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Solving the Radio Pollution

Reducing the amount of “radio pollution” is key to both coverage and capacity

Spectral efficiency is directly linked to the dominance of the best serving sector (i.e. focus on in-cell noise rather than out of cell noise)

With a 1:1 re-use model, physical antenna parameters are the only efficient mean to reduce radio pollutionThis translates into very significant post-design optimization effortsGiven that the propagation characteristics can only be somewhat influenced by antenna parameters, it also means that the optimization process will not be able to improve performance as much as it could if initial sites where selected on the basis of their radio characteristicsUltimately, there are cases where the only way to correct major pilot pollution problems is to shut down the polluter. This is indeed something to avoid post rollout


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Dual-Band Antennas and Impact on Design

When using multi-band antennas, it introduces additional design & optimization constraints for both WCDMA and GSM

The antennas offer limited per-band adjustments (electrical tilt only)Unless dual or tri-band antennas are already installed, existing GSM antennas need to be replaced

Typically, operators will want to deploy the WCDMA network without substantially impacting the GSM KPIs

Over-the-years optimization of GSM parameters is leading to solid KPIs. Change in radiation characteristics can affect (often negatively) the network performancePerformance of GSM1800 is more difficult to guarantee given thatthe only freedom for UMTS optimization is the electrical tilt, which is often shared with GSM1800


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Optimization for Multi Band in a 1:1 Re-Use

Despite the limitations, there are essentially three options:Optimize the WCDMA network and GSM1800 and possibly even GSM900 simultaneously (co-optimization)

Requires very advanced software and makes the optimization process quite complexMakes the rollout of optimization changes more difficult (need to coordinate between two technologies)

Optimize the WCDMA network and assess GSM performance to manage coverage impact

This actually makes sense since in general, there is a reasonable correlation between the performance of a WCDMA network and a GSM network (i.e. making one work better leads to the other one working better)The primary factor to look for is downtilt since WCDMA optimization will typically lead to stronger downtilts than GSM would like (soft handover and need to reduce pilot pollution leads to more aggressive down-tilting in WCDMA)

Optimize WCDMA layer with constraints on the optimizationThis indeed makes sense if dual-bands antennas are not used everywhere


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Site selection & density is directly driven by coverage objectivesDensity is therefore as variable as are the coverage objectivesSite selection and their parameters are based on their ability to contribute positively to the 3G network (i.e. doesn’t assume a 2G site is a good 3G site)

AdvantagesLowest possible CAPEX/OPEX costWorst polluters are inherently not re-usedAllows for better control of the coverage objectivesProvides a better mean to deal with site availability issuesCan deal better with a dynamic environment (i.e. problems with site acquisition, optimization constraints…)

DisadvantagesMore complex process – almost certainly requires better toolsImplies there is an acknowledgment that deploying a WCDMA network makes the design process even more dynamic

Progressive Overlay Approach

3G Roll-Out Philosophy: Progressive Overlay

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What is a Coverage Objective?

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35 40 45 50

Voice Service CoverageOutdoor CPICH Coverage144kbps Service CoverageIndoor CPICH Coverage

Implicit coverage objective of a 1:1 re-use Number of sites

Ser

vice

Pen

etra

tion

(%)

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Progressive Overlay Rollout Process

Define list of potential candidate sites within service

area (140 sites)

Create nominal configuration for all

candidate sites

Determine number of required sites

(100 sites)

Establish short list of “most valuable

sites”(20 sites)

Service areas are defined with specific service objectives in mind by marketing (E.g. 90% 144 kbps indoor coverage for Paris Intra Muros)

Define initial likely configuration and constraints for all possible candidate sites


Define coverage objectives

(Marketing)

Verify availability of the most valuable

sites

Re-assess nominal plan and confirm

sites required (which sites and

how many)

Define new list of most valuable additional sites(20 more sites)

Have we reached coverage

objectives?No

Yes

Possible candidate sites would typically be the existing GSM sites + other available sites

Estimate CAPEX requirements (i.e. site count) to fulfill the coverage objectives while considering design constraints

Based on the reference scenario, find out the 20 sites that provides the best overall coverage contribution

Output: reference scenario

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Process IllustrationPossible candidate site (GSM site or other

possibly available site)Set of Possible Candidate Sites

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Process Illustration

Site selected in initial reference scenario (which achieves the coverage objectives)

Creation of initial reference scenario

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Process Illustration

New site required due to a site not being available

Site is not required anymore

Site is not available anymore

When a site is not available, update reference scenario

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Site Potential Analysis

2

1

3

2

1

1

2

1

1

Priority (1-3)

11.585Site16

9.785Site3

6.890Site4

13.190Site5

10.495Site2

12.695Site8

9.6100Site7

10.5100Site6

14.2100Site10

Coverage (Erlangs)

Importance (%)Site

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Overall UMTS Roll-Out Process

Progressive Overlay Approach

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Pre/Post Launch Optimization

During Pre-Launch OptimisationNo traffic in the network, no subscribersNetwork typically tuned only based on drive test dataLabour intensive with repeated drive testA combined measured/predictive solution is best suited to provide solid initial design and reduce manpower

During OptimizationCommercial traffic, subscribers using the networkStatistics used to monitor network performance (KPIs)Drive testing just in casePost roll-out network optimization is an ongoing process, unlike pre-launch optimization

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Pre/Post Design OptimizationNetwork Quality Analysis

0.4

10.8

40.5

48.2

0.00.24.7

30.8

63.2

1.10.03.0

26.0

69.6

1.50.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

-99 to -18 -18 to -15 -15 to -12 -12 to -9 -9 to 0

Ec/Io (dB)

Perc

enta

ge o

f the

are

a

Initial GSMRoll-Out PlannerOptimizer

1:1 Re-Use

Progressive overlay

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Conclusions

Progressive Overlay Provides Substantial AdvantagesBetter aligned with business objectives

Ability to deploy a network with variable coverage objectives

Lower initial CAPEXAbility to deploy equipment more progressively, as traffic load is raising

Provides a better link between the site acquisition and design activitiesEasier to optimize network once loaded

Software Solutions are a EnablerProgressive overlay increases the complexity of some tasks but automated solutions substantially reduce manpower required.Automated solutions can improve both time to market and quality of initial network.

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Questions?

[email protected]

Tel: +1 613 271 5601www.marconi.com/wireless

Documents

3G Network Roll-Out Vision, Challenge and · PDF file3G Network Roll-Out Vision, Challenge and Solution ... Makes it difficult to have various coverage ... factor to look for is downtilt